UFC 3-270-04
15 March 2001
4.6. Subgrade and Base Preparation. After the deteriorated and loose concrete has been
removed, the base course should be examined. All disturbed material should be removed and
the patch area compacted (Figure 4.11.). If excessive moisture exists in the repair area, it should
be removed or dried before replacing. It is difficult to adequately compact granular material which
may result in settlement of the patch. Replacing some or all disturbed base material with lean
concrete or flowable fill may be the best alternative.
4.7. Dowel and Tiebar Placement. In repair of jointed concrete pavements, good load transfer
across the transverse repair joints appear to be the most ciritical factor affecting full-depth repair
performance. Load transfer is best achieved by properly installed dowel bars of sufficient size
and number. Dowels provide load transfer across repair joints while at the same time allowing
the joint to open and close as the surrounding pavement expands and contracts in response to
temperature and moisture changes. Hence, they are used in joints between slabs. In constrast,
tie bars provide both load transfer and prevent movement at the repair interface. Consequently,
tie bars are appropriate for repairs with a slab where the structural integrity of the slab is being
maintained. Since in repair, both dowels and tie bars have a load transfer role, their dimensions
and spacing should be selected based on the design loading. Note that tie bars in joints in new
construction function only to restrict movement at the joint, and they are typically relatively small
(#5 bar) and widely spaced [30 inches (750 millimeters)]. Both smooth steel dowels
(Figure 4.12.) and deformed reinforcement, tie bars, (Figure 4.13.) can be provided in the patch
joint. This is accomplished by drilling holes at specified locations into the exposed face of the
existing slab. Equipment is available to drill multiple holes simultaneously (Figure 4.14.). The
holes should be drilled by placing the drills in a rigid frame to prevent the drill bit from wandering
and holds them in a horizontal position at the correct height (one-half the slab thickness). The
depth of the holes should be approximately one-half the length of the dowel or tie bar.
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